1. Field of the Invention
The present invention relates to a method for filling a trench with a metal layer and a semiconductor structure formed by using the same, and more particularly, to a method including at least two deposition processes for filling a trench with a metal layer and a semiconductor structure formed by using the same.
2. Description of the Prior Art
Micro-processor systems comprised of integrated circuits (IC) are ubiquitous devices in modern society, being utilized in such diverse fields as automatic control electronics, mobile communication devices and personal computers. With the development of technology and the increasingly imaginative applications of electrical products, IC devices are becoming smaller, more delicate and more diversified.
Along with the miniaturization of the IC device, however, manufacturers have encountered problems related to IC fabrication methods. For example, aluminum is material commonly used for manufacturing metal gates. In a conventional gate-last process, after a dummy gate is formed, the dummy gate is removed to form a trench where aluminum is filled therein to form a metal gate. Due to the shrinkage of the device size as a consequence of device miniaturization, it is increasingly difficult to fill the aluminum into the trench. In some cases, a void may be formed within the trench. In addition, the aluminum layer formed by current deposition process has larger grain size, resulting in roughness of the surface, which is prone to spikes into the underlying barrier layer and even the work function metal layer. Consequently, the quality of the device is decreased.